The present invention relates to a lance for spraying particulate refractory-forming combustible material, particulate refractory material and a comburent gas. The invention extends to apparatus including such a lance and also to a method of spraying using such a lance.
Such lances are useful inter alia in performing spraying processes for forming refractory masses in situ for example using apparatus described in British Patent Specification No. 1330895 and counterpart U.S. Pat. No. 3,800,983.
In such processes, a mixture of refractory-forming particles and refractory particles is projected against a surface in a gas stream containing oxygen. Examples of refractory materials cited are particles of silica, alumina, zircon, zirconia and magnesia, and mixtures of two or more of these materials. Examples of refractory-forming materials are particles of silicon, aluminium, zirconium and magnesium, and mixtures of two or more of these materials. The refractory-forming particles react exothermically in the presence of oxygen to form a corresponding refractory material and to evolve heat to melt at least the surfaces of the refractory particles they are sprayed with, so that a coherent refractory mass is formed.
Such processes are particularly suitable for the hot repair of furnaces and other refractory devices and are especially advantageous where hot rebricking presents significant problems. It will be appreciated however that it is desirable that any such repair should be completed as rapidly as possible so that the down-time of the plant being repaired is minimized. It has been found when using known equipment for flame spraying to form a refractory mass that the rate at which a coherent mass of satisfactory quality can be built up is limited. This is especially disadvantageous when a large repair volume is required.